1. Field of the Invention
The present invention relates to image acquisition devices used in optical apparatuses, such as microscopes.
This application is based on Japanese Patent Application No. 2011-189659, the content of which is incorporated herein by reference.
2. Description of Related Art
In microscope observation, high-quality (high-resolution) images are required when performing pathological diagnosis based on the condition of cells or when acquiring images for detecting changes in a sample based on weak fluorescence. As means used for acquiring images, image acquisition devices employing image acquisition elements, such as CCDs, have been used in place of image acquisition devices employing conventional silver-salt films as image acquisition media (for example, see the U.S. patent application, Publication No. 2003/0117523 A1 and the Publication of Japanese Patent No. 4466394).
An image acquisition device disclosed in the U.S. patent application, Publication No. 2003/0117523 A1 includes a solid-state image acquisition element for acquiring an image of an object to be observed, cooling means for cooling the solid-state image acquisition element, and a printed board for electrical signal wiring. The printed board serves as a portion of sealing means for sealing the solid-state image acquisition element and the cooling means. A displacement member for moving the solid-state image acquisition element with a low pixel count over a two-dimensional plane extending perpendicularly to the optical axis is provided inside the sealing means.
With this configuration, the solid-state image acquisition element can be connected to an external unit outside a camera via the printed board serving as a portion of a closed container, thereby eliminating the need to use a sealing cable. Specifically, a board configuration that is not limited by the current-carrying capacity is achieved while also reducing dark-current noise and preventing condensation.
Furthermore, since the number of pixels in an acquired image is increased by moving the solid-state image acquisition element using the displacement member, the amount of observation light per pixel can be increased, thereby allowing for an increased number of pixels in an observation image without reducing the sensitivity.
An image acquisition device disclosed in the Publication of Japanese Patent No. 4466394 includes an outer housing that forms a first closed chamber sealed from outside air by an O-ring, an inner housing that forms a second closed chamber sealed from the first closed chamber, and an image acquisition element and a Peltier element disposed within the second closed chamber. Since the second closed chamber has a double-walled structure sealed from the outside air, the amount of moisture in the outside air entering the chamber can be reduced.
This configuration makes it difficult for the moisture contained in the outside air to enter the second closed chamber, thereby preventing performance degradation and reduced lifespan of the image acquisition element and the Peltier element.
In order to cope with design limitations and various applications, a camera attachment section of a microscope is disposed in various locations, such as the upper surface, the front surface, the bottom surface, or the side surfaces of the microscope. Because the installation space for a camera is limited, it is preferable that an image acquisition device including the camera be made as small as possible. Of various types of microscopes, stereomicroscopes are often incorporated in production lines. Therefore, it is desirable that the image acquisition device be as small as possible. Furthermore, in another proposed example of a microscope in the related art, functional components, such as the image acquisition device and an objective lens, are disposed within a single housing instead of being attached to the microscope afterwards. Due to these circumstances, there is an increasing demand for reducing the size of the image acquisition device.
On the other hand, there is an increasing demand for higher image quality and higher sensitivity in microscope observation for performing pathological diagnosis based on the condition of cells or for acquiring images for detecting changes in a sample based on weak fluorescence.
In the image acquisition device disclosed in the U.S. patent application, Publication No. 2003/0117523 A1, the displacement member, which requires a large space, is provided for achieving both high sensitivity and high pixel density. This displacement member is disposed within the closed container. The size of the image acquisition device is limited by the size of the closed container.
In the image acquisition device disclosed in the Publication of Japanese Patent No. 4466394, the first closed chamber is disposed outside the second closed chamber. The size of the image acquisition device is limited by the space in the closed container and the thickness of the components.